What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The most important link in the development and design of fasteners is quality control. There are several major points from the feed to the finished product shipment, and these major points have different inspection methods. First of all, the feed is related to appearance, size, elements, performance, detection of harmful substances, etc.; the process is more about appearance, size, percussion test, forging flow line; heat treatment is more about appearance, hardness, torque, tension , metallography, etc.; the surface treatment is more about some hydrogen embrittlement tests, coatings, salt spray, etc., including a detection of harmful substances in shipments. In size and appearance inspection, the common ones are quadratic element, contour measuring instrument, three-coordinate measuring instrument, image sorting machine (this is a full selection machine); in mechanical and chemical inspection, there are mainly hardness machines (Rockwell and Vickers). ), tensile machine, metallographic microscope; in material testing, there is a spectrum analyzer and a salt spray testing machine.
Standard spring washer (GB/T93-1987) Light spring washer (GB/T859-1987) Heavy spring washer (GB/T7244-1987) Spring washer is also known as spring meson. Saddle spring washer (GB/T 7245-1987) Saddle spring washer (GB/T 860-1987) Wave spring washer (GB/T 7246-1987) Wave spring washer (GB/T 955-1987)
Yueluo relates to a self-tapping screw according to the preamble of claim 1. A self-tapping screw is known from EP0623759B1, the ratio of the outer diameter to the smaller diameter of the self-tapping screw is about 1.25-1.5, the ratio of the outer diameter to the pitch lead is about 1.5-1.6 and the thread The flank angles of , are < 50° and ≥ 35°. EP0433484B1 proposes a self-tapping screw whose thread is provided with cutting teeth of approximately arcuate design, and the cutting edge and the thread crest are at the same horizontal position and are set in opposite directions. One purpose of Yueluo is to realize a general type of self-tapping screw so that it can be screwed particularly easily into holes drilled in concrete or other materials such as bricks and the like. According to Yueluo, this object is achieved by the features in the characterizing part of claim 1, and surprisingly, it has been found that the parallel arrangement of the flanks, ie with a flank angle of about 0°, will make screwing particularly easy when screwing in , especially if the diameter of the hole varies within an allowable tolerance. One reason may be due to the fact that there is no lateral pressure on the material screwed into the thread, even if threads of different depths are cut in concrete or other materials such as brick, chipped plywood, or hardwood. The thread cuts into the material over its entire width by cutting grooves. In particular according to the embodiment of claim 3 the material cut out when screwing in the screw can be discharged without any accumulation, the dependent claims reflecting many advantages of further embodiments.
Many parts on the car need to be rubberized, which can reduce noise, especially the parts related to shock absorption. Nuts are welded on many of these parts to facilitate the installation of other parts on them. The sheet metal is generally relatively thin, and most of them are only one or two millimeters. A through hole is punched, and then the nut is placed in the hole, and then around it. Spot welding is done so that it can be fixed. After spot welding, the periphery of the screw hole on the sheet metal will not be flat due to thermal deformation, which will affect the appearance.
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